Question

Calculate the molecules present in 90 g of H₂O.

• A. 10x 6.022 × 10²³
• B. 10
• C. 5
• D. 5x 6.022 × 10²³

Answer 1

Answer:

D. 5x 6.022 × 10²³

To calculate the number of molecules present in 90 g of H₂O, we need to follow these steps:

• Calculate the number of moles of H₂O :

  The molecular weight of H₂O is 18 g/mol. We can calculate the number of moles as follows:

Number of moles = mass of H₂O / molecular weight of H₂O
= 90 g / 18 g/mol
= 5 mol

• Calculate the number of molecules using Avogadro's number :

Avogadro's number is 6.022 × 10²³ molecules/mol. We can calculate the number of molecules as follows:

Number of molecules = number of moles × Avogadro's number
= 5 mol × 6.022 × 10²³ molecules/mol
= 3.011 × 10²⁴ molecules

Therefore, there are approximately 3.011 × 10²⁴ molecules present in 90 g of H₂O.